WASHINGTON
— In May 2004, just weeks after the images of abuse at Abu Ghraib had become public, the commanding officer of American forces in the Middle East sat before Congress and shared what he considered to be a bedrock tenet of military leadership.

"Officers of the United States military are responsible," said Gen. John Abizaid. "Every officer is responsible for what his or her unit does or fails to do."

Yet two years later, as the military nears the end of its efforts to prosecute those who staged the Abu Ghraib photographs, the responsibility for those crimes has fallen almost entirely on the lower ranks - at least publicly. The question of why has in many respects far overshadowed the rest of the legal process.

The reasons are many and begin with the obvious: Those who commit the crimes - on film, no less - are the easiest to snare. Yet many experts add that the lesson of the courts-martial of Abu Ghraib is: Once war's chaos descends, it becomes ever more difficult to trace the line of accountability upward through the ranks.

In this case, the confusion was not caused by bullets or bombs, but by the administration's decision to adopt new and undefined rules for detainee treatment before the war. With the new rules, the worst of war crept into the cellblock, and the chain of command all but evaporated.

"The fog of war does exist, and that's why you have to be so clear and drill, drill, drill," says Walter Huffman, who served as judge advocate general of the Army from 1997 to 2001. "When you inject uncertainty into a situation that was already filled with uncertainty, my experience is that this is exactly what happens."

Even in the best situations, establishing responsibility along the chain of command is among the thorniest of tasks for the military, whether the incident involves a ship run aground or a bungled battle plan. With Abu Ghraib, those bearing the public blame - and the jail time - have been enlisted men and women.

Last week, the 10th court-martial connected to Abu Ghraib concluded. As in every other case, the defendant was convicted and was not higher than the rank of staff sergeant. One final court-martial remains in May, also for a sergeant.

In some respects, that is typical, not least because soldiers on the ground are more likely than officers behind the lines to commit obvious war crimes. Yet experts note that officers are not exempt from discipline: It just comes in a different form.

Abu Ghraib has followed that pattern. The two highest-ranking officers known to be punished in connection with the scandal - Brig. Gen. Janis Karpinski and Col. Thomas Pappas - were given nonjudicial punishments that seriously blighted their careers. As a rule, though, nonjudicial punishments are not a matter of public record and therefore bring less attention than courts-martial.

To some, it is similar to what might happen to a police chief if he doesn't watch over his officers on the beat. "We do not yet hold people criminally responsible based on position alone," says William Eckhardt, who was the chief prosecutor in the My Lai cases, where two US soldiers were tried for leading a massacre of Vietnamese villagers in 1968. "It seems like things are working the way they should be," he adds.

Others, however, look at the Abu Ghraib proceedings and wonder what happened to the real-life "A Few Good Men" moment - when a plucky defense lawyer connected the dots between the crimes of enlisted men and the commands of a senior officer.

"Defense counsels are pretty good at defending their clients," says Mr. Huffman. "I was anticipating more higher-ranking officers called as witnesses of the defense."

It points to the limitations of the court-martial, which can essentially only hold senior officers to account if they gave an express order to abuse detainees. But that, in itself, is significant: It suggests to Huffman that high-level orders for abuse could not have been pervasive, or else defense lawyers would have found out about it.

In fact, the only general officer called during one of the courts-martial was Maj. Gen. Geoffrey Miller, who first oversaw Guantánamo before taking control of US detention facilities in Iraq in 2003. General Miller took the uncommon step of invoking his right against self-incrimination to avoid testifying.

"That was awfully unusually for a general officer," says Huffman. "That in itself sends an unfortunate signal."

As a result, what has emerged from the Abu Ghraib proceedings is a portrait of a problem more systemic than individual, a Hydra in reverse - a monster not with many heads, but none.

Like the 10 courts-martial, for instance, 12 Pentagon investigations of detainee treatment convened since Abu Ghraib speak in expansive terms about the dereliction of senior leadership but offer almost no specifics. Yet there is widespread agreement among experts that those convicted of crimes at Abu Ghraib were not simply "a few bad apples," as the administration suggested.

Instead, they were the product of a culture of uncertainty and neglect that blurred the lines of accountability. Critics go further. One of the Pentagon investigations, by Vice Adm. Albert Church, "says misconduct was pervasive, therefore there can be no singular cause," says John Hutson, a former judge advocate general of the Navy. "I would say it does prove a singular cause - an arguably criminal lack of leadership."

It is a broad swipe at Pentagon leaders and the administration, but it also gets at the frustrations of some Americans. Mr. Hutson's concerns are about the detainee doctrine laid out at the highest levels of government, and he acknowledges that in such instances, holding senior leaders responsible isn't necessarily a legal exercise.

After the Navy went through the Tailhook sexual-harassment scandal, the Navy's senior leadership simply resigned.

Adds Eugene Fidell of the National Institute for Military Justice: "Some of the accountability is accountability that can only be achieved politically."